Casing centralizer



June 2, 1953 4 R. c. BAKER 2,640,544

' CASING CENTRALIZER Filed Dec. 27. 1949 IN V EN TOR. .tPEl/BEA/ C BAKEQ,

flrroavsys Patented June 2, 1953 CASING CENTRALIZER Reuben C. Baker, Coalinga, Calif-Z, assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application December 27, 1949, Serial No. 135,135

6 Claims.

The present invention relates to devices for centering casings, liners and similar well conduits in well bores.

An object of the present invention is generally to improve centering devices of the character above indicated. Another object of the invention is to provide a casing centralizer embodying outwardly bowed springs, in which the springs are subjected to a minimum bending moment and minimum deformation under extreme loading conditions.

A further object of the invention is to provide a casing centralizer that can be mounted easily on a casing string, to which a stop member is secured for pulling the centralizer through the well bore.

Still a further object of the invention is to provide a casing centralizer that can be easily mounted on the casing string on oppsite sides of a casing coupling collar, in order that the collar can function as a stop member for pulling the centralizer through the Well bore.

Another object of the invention is to provide an improved hinge type casing centralizer, in which the hinged portions can be secured together, after the centralizer has been mounted on the casing string, in a rapid and facile man ner.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation, with parts broken away, of a casing centralizer mounted on a string of casing, prior to running of the casing in the well bore;

Fig. 2 is a longitudinal elevational and sectional view, similar to Fig. 1, disclosing the casing string and centralizer in a well bore;

Fig. 3 is a cross-section taken along the line 33 on Fig. 1;

Fig. 4 is an enlarged fragmentary side eleva- "tion of one of the hinges forming part of the centralizer;

Fig. 5 is a longitudinal section taken along the line s-s on- Fig. 4,

substantially semi-circular pieces.

stop collar.

A casing centralizer A is illustrated in the drawings as mounted upon a casing string, which includes an upper casing section B, a lower casing section 0, and an intervening'coupling collar D threadedly secured to the opposed pin ends [0, ll] of the casing sections, in order to hold them rigidly together. In the specific form of the invention illustrated, the coupling collar D functions as a stop member, tending to pull the casing centralizer A through the well bore, regardless of the longitudinal direction of movement of the casing string therein.

The: casing centralizer includes an uppercage assembly II, that can be mounted on the upper casing section B above thecoupling collar D, and a lower cage'assembly [2, that can be mounted on the lower casing section C below the coupling collar D. These cage assemblies ll, l2 are secured to one another by intervening outwardly bowed leaf springs l3, which extend completely across the coupling collar or stop member D.

Each cage assembly H or l2 includes an outer spring annulus or collar [4 and an inner stop annulus or collar l5, these two collars being connected together by rigid interconnecting members or bars [6, whose inner and outer ends abut and are welded to the inside surfaces of the collars. Theinterconnecting bars 16 preferably do not extend laterally beyond the inner or outer surfaces of the collars [4, I5. Sufficient bars are provided, circumferentially spaced. from one another, to form a comparatively rigid cage assembly II and I2.

The outwardly bowed springs l 3 are preferably uniformly spaced around the cage members II, l2 and have their end portions l3a secured to the spring collars [4. As an example, the ends l3a may be disposed in inner notches H in the collars l4, and they may be welded to the spring collars, as by the aid of welding material 18 extending across their outer ends.

For the purpose of enabling the casing centralizer A to be mounted upon an assembled casing string Which already possesses a stop member, such as the coupling collar D, each cage member is made sectional, with its spring collar 14 and stop collar l5 composed of two main or These pieces can be secured together by hinges I9, 20 to form a circumferentially continuous spring collar and As disclosed in the drawings, at one side of the cage the two parts of the spring collar [4 aresecured to one another by a hinge 19. The leaves 2 l of the hinge are spot welded, or other- "wise'suitablys'e'cured, to the outer surface of the collar sections, whereas the knuckle or barrel portions 22 of the hinge are interleaved with respect to one another, and are disposed between the adjacent ends of the collar sections. A suitable hinge pin 23 extends through the knuckles 22, to pivotally secure the collar sections to one another.

A similar hinge arrangement is provided on the same side of the cage for the stop collar l5. The hinge arrangements are provided on both the upper and lower cages, the hinges Hi all being in alignment with one another; so as to enable the centralizer to be swung between open and closed positions about the hinge axis of the pins 23 in mounting the centralizer on the casing string, with the upper and lower cages l I, 12 on opposite sides of the coupling collar D.

The other side of the cages H, l2 are similarly provided with hinges 20 in alignment with one another, the hinge leaves 2! being spot welded, or otherwise suitably secured, to the exteriors of th collars I l, l and the knuckles or barr ls 22 being disposed between the adjacent ends of the collar sections.

h hin e pins 23. at one. side of the casing centralizer are in place and form the pivotal axis for swinging the casing centralizer between open and closed positions. The other hinge members 20 originally do not have a hinge pin extending through their interleaved barrel portions 22. After the centralizer has been swung to open position about the hinge axis on one side containing the hinge pins 23, and has been placed around the casing string, it can be swung to closed position with the barrels 22 of the hinges 2c interleaved with respect to one another. A pin 25 may then be inserted within the knuckles 22 of each hinge 20, fer the purpose of holding the collars l4, 15 of the cages l, L2 snugly around the casing sections B, (2, in slidable relation with respect thereto.

A rapid assembly can be made by constituting each of the lastementioned hin e pins 25 as a drive screw or nail, whose shank 26 has steeply pitched, helically arranged ribs 2] that are adapted to cut grooves in the inner surfaces of the barrel portions 2| of the hinge 20, Each drive screw has a head 28 at one end Of the shank and a tapered point 2.9 at the other end of the shank. The point of the drive screw is inserted in the outer knuckle 22 of a hinge 2 and t h ad 8 struck y a hammer.- T e tap re p i 29 automatically aligns all of the knuckle members 22 with respect to each other, and the he al ri es or threads 21 cause he sc ew t turn slightly as the companion groove is formed in the knuckles 22. A tight fit is insured when the drive screw 25 is driven into the hinge members 2|, the pin 25 remaining firmly in pla e du ing u of the centering device in the well bore.

The drive pins 25 for the spring collars I4 may be inserted through the knuckles 2] in either an upward or a downward posi ion. H Q 11 the length of the coupling collar D is preferably only slightly less than the distance between the stop collars 15, the drive screw or pin 25 for the lower stop collar l5 must be inserted through the knuckles 21 of the lower stop collar hinge 20 in an inverted position, inasmuch a sufficient clearance may not remain between the coupling collar D and the lower stop collar [5 to allow insertion of the drive screw through the upper end of this hinge. Regardless of the direction in which any of the drive screws are inserted through the hinge, they cut their own threads on the hinge knuckle, members 22, and hold the assembly permanently in place on the casing string.

Each cage assembly H, 12 is relatively long. As disclosed in the drawings, a cage assembly may be approximately one-third of the over-all length of the casing centralizer. Such elongate cage assembles are preferred, so as to dispose the stop collar members l5 closer to the central portions l3b of the leaf springs [3. They also result in the disposition of the stop or coupling collar member D opposite the central portions [3b of the leaf springs. This arrangement is preferred, since it provides a minimum interference with the inward collapsing of the springs to the maxie gtent, and places a minimum of deformation on the springs [3 under extreme loading conditions, as when the springs are pressed inwardly to their fullest extent against the casing string.

After the as ng cent lizer A has been m unted on the casing s ring, the com nation i lowered through the well bore. During this lowering movemen he cou l n cellar D ngages th lower s op ce la the wnward movement o force being transmitted through the rigid bars or o umns 6 t the lower sp ing collar l4- Sin he lower ends we of the springs are firmly s red to the lower spri c l r he prin s 13 will be pulled through the well bore, and through any restrictions that might be encouner d her in. When a res riction or tight place i n un er d, the prings are ur ed inwardly tod t e asin string, which Shifts the upper c se H relatively in an upward d rection away from the coupling collar D.

In. a m la mann r, upward movement of h casing str ng w ll cause th coupling m m r D o enga e the p er step co ar 15, in order to xe a ull ng act on n the outwardly bowed spring mem ers l3, wh ch iacilitates their passa e through a well bore and through any restrictions h re n ha might be encountered.

Y mak ng e cage H, l2 rela ively lon the stop collars l5 re ught closer to the central portions 13b of the outwardly bowed spring memb As a result, th sprin s, mu be deflected inwardly, under high loading conditions, to a substantial extent before a portion of each sprin as the part w ll en a e h top coll r 5.. h u e agem n oc urs, a b nd n m ment s plac d on a spring ni m I I3, tend ng o de form we e such bending moment is relatively small n the casing c ntraliz r illustrat d, ce th placing of the st p ellar l5 close to the central portion I 317 of the spring reduces the moment arm of the inward force urging the spring toward the casing. In addition, the m un of the force tending to b nd the sprin I3 about the stop collar I5 is less, inasmuch as the sprin is almost in its fully collapsed position beiore it enga es the stop collar member l5.

It is also to be noted that the spring does not engage the stop member or coupling collar D itself, until the spring has been almost completely flattened against the casing string. As a result, there is very little opportunity for binding of the sprin upon the stop collar, which binding might tend to prevent rotation of the casing string within the centralizer A whenever Such rotation is desired. If the springs were to bind upon the s p c llar, r t ion of the casing string might tend to rotate the leaf springs l3 with it, with potential dama t th c ntr lizer devi From the foregoing description, it is apparent that a casing centralizer has been provided that can be mounted on-assembled casing sections B,

C and which can utilize the casing coupling col-,

lar D as a stop member for pulling the centralizer through the well bore, regardless of the direction of longitudinal movement of the casing string. Of course, other stop collars or rings than the coupling collar D can be used, if desired, the centralizer being easily mounted on the casing section merely by first opening it about the axis of the hinges l9, and then moving it to closed position, with the cages H; I2 on opposite sides of the stop member, whereupon the centralizer can be unitized by forcing the drive screws 25 through the knuckles 22 of the hinges 20 on the side of the centralizer opposite the permanently hinged side. The springs can be loaded to an extreme condition before they will engage the stop members or collars D, and, even when so engaged, the bendin moment is comparatively small, so as to avoid permanent deformation of the springs l3, and the tendency for their breaking as a result of being bent around other members, such as the stop rings I5. In addition to the foregoing, the stop member D, which can be made of one or a plurality of parts, is held to a position substantially midway along the centralizer and is only engaged by the springs l3 when they are under extreme loading conditions. Such midpositioning of the stop member D is assured by making the spacing between the stop collars l5 of the cages ll, 12 only slightly greater than the length of the stop member D itself.

The inventor claims:

1. In a centering device for well conduits: an upper cage assembly; a lower cage assembly; each assembly including an outer collar, an inner stop collar, and circularly spaced substantially rigid bars interconnecting said outer and inner collars; circumferentially spaced outwardly bowed leaf springs having their upper and lower ends immovably secured to the outer collars on said upper and lower cage assemblies, respectively; and stop means between the inner stop collars of said upper and lower cage assemblies; the distance between said inner stop collars being slightly greater than the length of said stop means; said stop collars being disposed adjacent the medial portions of said leaf springs and normally spaced inwardly away from said leaf springs.

2. In combination: an upper conduit section; a lower conduit section; a coupling interconnecting said sections; an upper cage assembly on said upper section above said coupling; a lower cage assembly on said lower section below said coupling; each assembly including an outer collar, an inner stop collar adjacent said coupling and circularly spaced substantially rigid bars interconnecting said outer and inner collars; circumferentially spaced outwardly bowed leaf springs having their upper and lower ends immovably secured to the outer collars of said upper and lower cage assemblies, respectively; the distance between said inner stop collars being slightly greater than the length of said coupling; said stop collars being disposed adjacent the medial portions of said leaf springs and normally spaced inwardly away from said leaf springs.

3. In a centering device for well conduits: an upper sectional cage assembly; a lower sectional cage assembly; each assembly including an outer sectional collar, an inner sectional stop collar, and circularly spaced bars interconnecting said outer and inner collars; ciroumferentially spaced outwardly bowed leaf springs having their upper 6 and lower ends immovably secured to the outer collars of said upper and lower cage assemblies, respectively; a hinge securing the sections of each stop collar together at one side of the device; a hinge securing the sections of each outer collar together at said one side of the device; said hinges all being coaxial; means securing the respective sections of each stop collar and of each outer collar to each other at the opposite side of the device; stop means between the inner stop collars of said upper and lower cage assemblies; the distance between said stop collars being slightly greater than 'the length of said stop means; saidstop collars being disposed adjacent the medial portions of said leaf springs and normally spaced inwardly away from said leaf springs.

4. In a centering device for well conduits: an upper sectional cage assembly; a lower sectional cage assembly; each assembly including an outer sectional collar, an inner sectional stop collar, and circularly spaced bars interconnecting said outer and inner collars; circumferentially spaced outwardly bowed leaf springs having their upper and lower ends immovably secured to the outer collars of said upper and lower cage assemblies, respectively; a hinge securing the sections of each stop collar together at one side of the device; a hinge securing the sections of each outer collar together at said one side of the device; said hinges all being coaxial; hinge means securing the respective sections of each stop collar and outer collar to each other at the opposite side of the device, said hinge means including hinge elements attached to the sections of each stop collar and each outer collar, and a drive screw forced through adjacent hinge elements at each collar; stop means between the inner stop collars of said upper and lower cage asemblies; said stop collars being disposed adjacent the medial portions of said leaf springs and normally spaced inwardly from said leaf springs.

5. In a centering device for well conduits: an upper sectional cage assembly; a lower sectional cage assembly; each assembly including an outer sectional collar, an inner sectional stop collar, and circularly spaced bars interconnecting said outer and inner collars; circumferentially spaced outwardly bowed leaf springs having their upper and lower ends immovably secured to the outer collars of said upper and lower cage assemblies, respectively; a hinge securing the sections of each stop collar together at one side of the device; a hinge securing the sections of each outer collar together at said one side of the device; said hinges all being substantially coaxial; means securing the respective sections of each stop collar and of each outer collar to each other at the opposite side of the device; stop means between the inner stop collars of said upper and lower cage assemblies; said stop collars being disposed adjacent the medial portions of said leaf springs and normally spaced inwardly from said leaf springs.

6. In combination: an upper conduit section; a lower conduit section; a coupling interconnecting said sections; an upper sectional cage assembly on said upper section above said coupling; a lower sectional cage assembly on said lower section below said coupling; each assembly including an outer sectional collar, an inner sectional stop collar, and circularly spaced bars interconnecting said outer and inner collars; circumferentially spaced outwardly bowed leaf springs having their upper and lower ends immovably secured to the outer collars of said upper and lower cage assemblies, respectively; a hinge so.- ouring the sections of each stop collar together at one side of the device; a hinge securing the sections of each outer collar together at said one side of the device; said hinges all being substantially coaxial; means securing the respective sections of each stop collar and of each outer collar to each other at the opposite side of the device; the distance between said inner stop collars being slightly greater than the length of said coupling; said stop collars bein disposed adjacent the medial portions of said leaf springs and normallyspaced inwardly from said leaf springs. REUBEN C. BAKER.

' References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Rouxel Jan. 19, 1915 La Velle Aug. 19, 1930 Hartman Aug. 25, 1931 Boyd Jan. 31, 1939 Welles Jan. 14, 1941 Welles Jan. 14, 1941 Hartman et a1. July 21, 1942 Clark, Jr. July 24, 1951 

